J/MNRAS/506/2122 Light curves and eclipse times of HW Vir (Brown-Sevilla+, 2021)
A new photometric and dynamical study of the eclipsing binary star HW Virginis.
Brown-Sevilla S.B., Nascimbeni V., Borsato L., Tartaglia L., Nardiello D.,
Granata V., Libralato M., Damasso M., Piotto G., Pollacco D., West R. G.,
Colombo L.S., Cunial A., Piazza, G., Scaggiante F.
<Mon. Not. R. Astron. Soc. 506, 2122 (2021)>
=2021MNRAS.506.2122B 2021MNRAS.506.2122B (SIMBAD/NED BibCode)
ADC_Keywords: Binaries, eclipsing ; Stars, subdwarf ; Photometry, CCD
Keywords: binaries: eclipsing - stars: individual: HW Vir - planetary systems -
planets and satellites: dynamical evolution and stability -
techniques: photometric
Abstract:
A growing number of eclipsing binary systems of the HW Virginis (HW
Vir) kind (i.e. composed by a subdwarf-B/O primary star and an M dwarf
secondary) show variations in their orbital period, also called
eclipse time variations (ETVs). Their physical origin is not yet known
with certainty: While some ETVs have been claimed to arise from
dynamical perturbations due to the presence of circumbinary planetary
companions, other authors suggest that the Applegate effect or other
unknown stellar mechanisms could be responsible for them. In this
work, we present 28 unpublished high-precision light curves of one of
the most controversial of these systems, the prototype HW Vir. We
homogeneously analysed the new eclipse timings together with
historical data obtained between 1983 and 2012, demonstrating that the
planetary models previously claimed do not fit the new photometric
data, besides being dynamically unstable. In an effort to find a new
model able to fit all the available data, we developed a new approach
based on a global-search genetic algorithm and eventually found two
new distinct families of solutions that fit the observed timings very
well, yet dynamically unstable at the 105-yr time-scale. This serves
as a cautionary tale on the existence of formal solutions that
apparently explain ETVs but are not physically meaningful, and on the
need of carefully testing their stability. On the other hand, our data
confirm the presence of an ETV on HW Vir that known stellar mechanisms
are unable to explain, pushing towards further observing and modeling
efforts.
Description:
Photometric data and derived eclipse times for 30 light curves listed
in Table 2 and 3, including 28 previously unpublished.
Objects:
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RA (2000) DE Designation(s) (Per)
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12 44 20.24 -08 40 16.8 HW Vir = BD-07 3477 (0.116719555)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 80 26 Log of observations
table3.dat 36 30 Best-fitting eclipse timings (T0) for the
primary eclipse of HW Vir derived from our
unpublished data
lcs.dat 92 117835 Light curves of HW Virginis
t0.dat 44 270 Eclipse times of HW Virginis
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See also:
J/AJ/137/3181 : HW Vir differential VR light curves (Lee+, 2009)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- ID Unique identifier
7- 16 A10 --- Date Evening date of the observation
18- 31 A14 --- Tel Telescope used
33- 37 I5 --- Nframes Mumber of acquired frames
39- 50 A12 --- Filter Photometric passband
52- 80 A29 --- PhaseCov Phase coverage, eclipses that were observed
among the primary and secondary
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 15 F15.7 d T0 Best-fitting eclipse time (TDB-based)
17- 25 F9.7 d e_T0 Error on best-fitting eclipse time
28- 32 I5 --- Epoch Epoch computed with respect to the linear
ephemeris in equation (1) of the paper
34- 36 A3 --- ID Unique identifier
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Byte-by-byte Description of file: lcs.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 F18.10 d BJD Barycentric Julian Day (TDB-based)
20- 28 F9.6 mag mag Magnitude in Filter, baseline-subtracted
30- 38 F9.7 mag e_mag Error on magnitude
40- 49 F10.6 mag magraw Magnitude in Filter, raw
51- 59 F9.6 --- Phase Orbital phase w.r.t. fitted T0
61- 63 A3 --- Code Light curve ID (matching Table 2)
65- 66 I2 --- CodeNum [0/29] Light curve ID (numerical)
68- 76 A9 --- Tel Telescope used
78- 81 A4 --- Filter Filter used (R, V, r, K2, WASP)
83- 92 A10 "date" Night Evening date of the night (1)
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Note (1): Some data sets cover more than one observing night:
for such cases NIGHT is set to 0000-00-00.
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Byte-by-byte Description of file: t0.dat
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Bytes Format Units Label Explanations
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1- 18 F18.10 d T0 Eclipse time (TDB-based)
20- 32 F13.11 d e_T0 Error on eclipse time
34- 39 I6 --- Epoch Ephemeris epoch
41- 44 A4 --- Dataset Dataset ID (matching Table 2)
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Acknowledgements:
Valerio Nascimbeni, valerio.nascimbeni(at)inaf.it
(End) Patricia Vannier [CDS] 19-Aug-2021